The present invention relates to an endoscope system in which a plurality of endoscopes of different kinds are interchangeably connected to a fluid (liquid, water, air or gas) source or sources common thereto.
For an endoscope it is well known that air and liquid can be supplied with a single nozzle disposed in opposed relationship to an observation window by joining an air supply line and a water supply line which are arranged within the insertable portion of the endoscope, at the distal end thereof. In addition, air or a non-inflammable gas is supplied through the air supply line to the interior of a coelom to expand the coelom and thereby obtain a spacing between the observation window disposed at the distal end of the endoscope and the coelom wall.
Such an air supply a suction operation essentially forms part of the inserting technique during an procedure with an endoscope, so that the flow rate of the air supply must be controllable for proper insertability of an endoscope. In addition, since an oversupply of air may pain to patient or damage of a coelom tissue, the control of the flow rate of air supply is essential in an operation of an endoscope. This means that it is desirable for endoscopes to be used in the same coelom to have supply air with the same flow rate even when they differ in kind.
As a matter of fact, the length and diameter of the insertable portion of an endoscope and, accordingly, the resistance of the fluid supply pipe line for fluid supply varies with the kind or use of the endoscope, so in that the flow rate of fluid supply per unit time varies. The prior art has failed to take this into account.
By way of example, even with the same kind of an endoscope, the air supply flow rate of air supply varies when the endoscope has its insertable portion of different length, and even in general-purpose scopes of the same kind for the upper digestive canal, a normal scope and a small-diameter scope differ in their air supply flow rates.
As such, it is inconvenient to use an endoscope having the insertable portion of a different length and diameter since it has fluid supply pipe lines in a different length and diameter and there is a different flow rate of the fluid supply due to the different resistance of the pipe line.
A conventional method for changing the flow rate of an air supply is shown in Japanese Utility Model Publication Sho 58/1983--No. 18884 in which the air supply flow rate is controlled by leaking part of the air from the air supply through a leakage hole that is changeable in size. It is extremely difficult, however, to precisely control the flow rate by the leakage method. Another method for changing an air supply flow rate of air supply is shown in Japanese Laid-Open Utility Model Publication Sho 59/1984--No. 64101 in which a pressure device comprising a cylinder and a piston, is provided in a supply line or on a tank. With this method, it is also difficult to precisely control the flow rate.
It is conceivable to change the flow rate fluid supply flow rate in each endoscope with the conventional methods described above. However, in such a case it is necessary to adjust the flow rate in the endoscope in accordance with the resistance of the fluid supply line, necessitating excessive expenditure of time and effort. Accordingly, it is desirable to provide improved endoscopes which have the same flow rate fluid supply per unit time even when endoscopes that differ in kind are used.
In addition, it is to be particularly desired that the air supply flow rates are unified in a colonoscope and a sigmoidoscope for the colon, and in an esophagoscope, gastroscope, duodenoscope, enteroscope and general-purpose scope for the esophagus to the duodenum, when they are used in the same coelom.
A physician can recognize the difference in air supply flow rates of between 1300 ml/min and 1700 ml/min. In other words, it may be said that this difference of 30 percent is unacceptable. Accordingly, the difference in air supply flow rates not exceeding 15 percent, which is the half of 30 percent, can be practically considered to be the same flow rate.
As for an absolute fluid supply flow rate of fluid supply, the optimum value depends upon physician's technical skill. For example, some physicians like a comparatively small of fluid supply flow rate of approximately 1000 ml/min, that is, giving priority to preventing a danger due to oversupply of fluid and some others like a comparatively large flow rate of approximately 1700 ml/min, that is, giving priority to reducing an inspection period. Accordingly, it is desirable that an absolute fluid supply flow rate is made variable as by using a variable fluid pump. For the case where an endoscope for the upper digestive canal is substituted for a colonoscope, it is also desirable that both endoscopes have the same flow rate.
While the flow rate of air supply, which varies with particular kinds of endoscopes, is approximately 1500 ml/min, the water supply flow rate is several tens ml/min at the most, so that there won't be any trouble, such as oversupply of water, due to variation of the water flow rate. However, when spraying and ejecting air simultaneously, air flow is at the same rate as when only air is supplied. When cleaning a lens surface of an endoscope by spraying water, it is necessary to supply a predetermined amount of water at a substantially constant rate. Because there is a possibility of causing an oversupply of air into a coelom when cleaning the lens surface because of variations in the water flow rate it is desirable to unify the flow rates water supply.